The present invention relates to manually operated grease guns for lubricating bearing surfaces found in automobile chassis as well as various types of industrial equipment. These hand grease guns have a cylindrical reservoir or body that holds heavy grease, and a dispensing head mechanism for the grease at one end thereof. This dispensing mechanism is essentially a piston operated by two-bar linkage mehanism. A spring biased follower assembly in the cylindrical body of the gun continuously urges the heavy lubricant toward the dispensing head of the gun and into a chamber that slidably receives the dispensing piston. As the operator withdraws the piston from the chamber, the follower assembly forces lubricant into the chamber, and thereafter the operator manually drives the piston into the chamber forcing lubricant from a suitable outlet port under high presssure to the part to be lubricated.
The lubricant is loaded into the cylindrical body of the lubrication gun in a variety of ways, and the follower assembly must be adaptable to the different loading methods employed. Firstly, the gun may be loaded with lubricant using bulk loading techniques. Pressure loading is one of these where lubricant under pressure is loaded through the dispensing head from a source of lubricant under high pressure. Another bulk loading technique is referred to as suction loading and this is done by drawing lubricant through the dispensing head by manually withdrawing the follower assembly and evacuating the gun cylinder. Lastly, bulk loading can be effected simply by hand-packing the cylinder with heavy lubricant.
Besides bulk loading, the lubrication gun can be loaded with a lubrication cartridge that consists of a sleeve open at both ends and prepacked with lubricant. With the end of the lubrication gun removed, the cartridge is slid into the gun cylinder and the end replaced.
With this background, it has been found extremely difficult to devise a follower assembly that will adequately seal in both a cartridge and the inner diameter of the cylindrical body since they of course have different inner diameters. This problem has in the past been approached in a variety of ways, none of which have been found satisfactory.
One technique is to use a guide to aid in entry of the follower from the cylinder bore to the cartridge bore, and of course that not only requires an additonal part, but also is difficult for the operator to use. Another approach is the design of a follower that seals in two different diameter bores by flipping or reversing an outer lip on the follower. While this has been somewhat satisfactory, it is also difficult for the operator to use since the operator must remove the follower to go through this reversing process.
A still further approach has been to provide a long axially extending outer wall that is very thin so that it can flex outwardly in different diameter bores. Such a construction is shown in the Chester Dorn pat. No. 3,655,101. The problem in this thin outer walled follower is that the wall must be supported at both ends to achieve the desired flexing action. To achieve this, Dorn provides a plurality of plates or washers at the forward end of the follower to keep the outer wall concentric with the axis of the follower rod and also to pull the outer wall forwardly. While this construction has been found satisfactory for cartridge and bulk loading use, it is difficult to manufacture and costly because of the many parts and washers required to support the thin outer wall.
It is a primary object of the present inventon to ameliorate the problems noted above in the prior art of follower assemblies for multiple loaded lubrication guns.